1. Field
The present disclosure relates generally to data networking and in particular to a backhaul system to manage and control multiple backhaul radios that connect remote edge access networks to core networks in a geographic zone.
2. Related Art
Data networking traffic has grown at approximately 100% per year for over 20 years and continues to grow at this pace. Only transport over optical fiber has shown the ability to keep pace with this ever-increasing data networking demand for core data networks. While deployment of optical fiber to an edge of the core data network would be advantageous from a network performance perspective, it is often impractical to connect all high bandwidth data networking points with optical fiber at all times. Instead, connections to remote edge access networks from core networks are often achieved with wireless radio, wireless infrared, and/or copper wireline technologies.
Radio, especially in the form of cellular or wireless local area network (WLAN) technologies, is particularly advantageous for supporting mobility of data networking devices. However, cellular base stations or WLAN access points inevitably become very high data bandwidth demand points that require continuous connectivity to an optical fiber core network.
When data aggregation points, such as cellular base station sites, WLAN access points, or other local area network (LAN) gateways, cannot be directly connected to a core optical fiber network, then an alternative connection, using, for example, wireless radio or copper wireline technologies, must be used. Such connections are commonly referred to as “backhaul.”
Many cellular base stations deployed to date have used copper wireline backhaul technologies such as T1, E1, DSL, etc. when optical fiber is not available at a given site. However, the recent generations of HSPA+ and LTE cellular base stations have backhaul requirements of 100 Mb/s or more, especially when multiple sectors and/or multiple mobile network operators per cell site are considered. WLAN access points commonly have similar data backhaul requirements. These backhaul requirements cannot be practically satisfied at ranges of 300 m or more by existing copper wireline technologies. Even if LAN technologies such as Ethernet over multiple dedicated twisted pair wiring or hybrid fiber/coax technologies such as cable modems are considered, it is impractical to backhaul at such data rates at these ranges (or at least without adding intermediate repeater equipment). Moreover, to the extent that such special wiring (i.e., CAT 5/6 or coax) is not presently available at a remote edge access network location; a new high capacity optical fiber is advantageously installed instead of a new copper connection.
Rather than incur the large initial expense and time delay associated with bringing optical fiber to every new location, it has been common to backhaul cell sites, WLAN hotspots, or LAN gateways from offices, campuses, etc. using microwave radios. An exemplary backhaul connection using the microwave radios 132 is shown in FIG. 1. Traditionally, such microwave radios 132 for backhaul have been mounted on high towers 112 (or high rooftops of multi-story buildings) as shown in FIG. 1, such that each microwave radio 132 has an unobstructed line of sight (LOS) 136 to the other. These microwave radios 132 can have data rates of 100 Mb/s or higher at unobstructed LOS ranges of 300 m or longer with latencies of 5 ms or less (to minimize overall network latency).
Traditional microwave backhaul radios 132 operate in a Point to Point (PTP) configuration using a single “high gain” (typically >30 dBi or even >40 dBi) antenna at each end of the link 136, such as, for example, antennas constructed using a parabolic dish. Such high gain antennas mitigate the effects of unwanted multipath self-interference or unwanted co-channel interference from other radio systems such that high data rates, long range and low latency can be achieved. These high gain antennas however have narrow radiation patterns.
Furthermore, high gain antennas in traditional microwave backhaul radios 132 require very precise, and usually manual, physical alignment of their narrow radiation patterns in order to achieve such high performance results. Such alignment is almost impossible to maintain over extended periods of time unless the two radios have a clear unobstructed line of sight (LOS) between them over the entire range of separation. Furthermore, such precise alignment makes it impractical for any one such microwave backhaul radio to communicate effectively with multiple other radios simultaneously (i.e., a “point to multipoint” (PMP) configuration).
In wireless edge access applications, such as cellular or WLAN, advanced protocols, modulation, encoding and spatial processing across multiple radio antennas have enabled increased data rates and ranges for numerous simultaneous users compared to analogous systems deployed 5 or 10 years ago for obstructed LOS propagation environments where multipath and co-channel interference were present. In such systems, “low gain” (usually <6 dBi) antennas are generally used at one or both ends of the radio link both to advantageously exploit multipath signals in the obstructed LOS environment and allow operation in different physical orientations as would be encountered with mobile devices. Although impressive performance results have been achieved for edge access, such results are generally inadequate for emerging backhaul requirements of data rates of 100 Mb/s or higher, ranges of 300 m or longer in obstructed LOS conditions, and latencies of 5 ms or less.
In particular, “street level” deployment of cellular base stations, WLAN access points or LAN gateways (e.g., deployment at street lamps, traffic lights, sides or rooftops of single or low-multiple story buildings) suffers from problems because there are significant obstructions for LOS in urban environments (e.g., tall buildings, or any environments where tall trees or uneven topography are present).
FIG. 1 illustrates edge access using conventional unobstructed LOS PTP microwave radios 132. The scenario depicted in FIG. 1 is common for many 2nd Generation (2G) and 3rd Generation (3G) cellular network deployments using “macrocells”. In FIG. 1, a Cellular Base Transceiver Station (BTS) 104 is shown housed within a small building 108 adjacent to a large tower 112. The cellular antennas 116 that communicate with various cellular subscriber devices 120 are mounted on the towers 112. The PTP microwave radios 132 are mounted on the towers 112 and are connected to the BTSs 104 via an nT1 interface. As shown in FIG. 1 by line 136, the radios 132 require unobstructed LOS.
The BTS on the right 104a has either an nT1 copper interface or an optical fiber interface 124 to connect the BTS 104a to the Base Station Controller (BSC) 128. The BSC 128 either is part of or communicates with the core network of the cellular network operator. The BTS on the left 104b is identical to the BTS on the right 104a in FIG. 1 except that the BTS on the left 104b has no local wireline nT1 (or optical fiber equivalent) so the nT1 interface is instead connected to a conventional PTP microwave radio 132 with unobstructed LOS to the tower on the right 112a. The nT1 interfaces for both BTSs 104a, 104b can then be backhauled to the BSC 128 as shown in FIG. 1.
As described above, conventional microwave backhaul radios have used “high gain” (typically >30 dBi or even >40 dBi) to achieve desired combinations of high throughput, long range and low latency in bridging remote data networks to core networks for unobstructed line of sight (LOS) propagation conditions. Because of their very narrow antenna radiation patterns and manual alignment requirements, these conventional microwave backhaul radios are completely unsuitable for applications with remote data network backhaul in obstructed LOS conditions, such as deployment on street lamps, traffic lights, low building sides or rooftops, or any fixture where trees, buildings, hills, etc., which substantially impede radio propagation from one point to another.
Additionally, such conventional microwave backhaul radios typically have little or no mechanism for avoiding unwanted interference from other radio devices at the same channel frequency, other than the narrowness of their radiation patterns. Thus, users of such equipment are often skeptical of deployment of such conventional backhaul radios for critical applications in unlicensed spectrum bands. Even for common licensed band deployments, such as under the United States Federal Communications Commission (FCC) Part 101 rules, conventional backhaul radios are typically restricted to a particular channel frequency, channel bandwidth and location placement based on a manual registration process carried out for each installation. This is slow, inefficient, and error prone as well as wasteful of spectrum resources due to underutilization, even with the undesirable restriction of unobstructed LOS conditions.
Furthermore, once deployed in the field, conventional microwave backhaul radios are typically islands of connectivity with little or no capability to monitor the spectrum usage broadly at the deployment location or coordinate with other radios in the vicinity to optimally use spectrum resources.
FIG. 2 illustrates an exemplary deployment of multiple conventional backhaul radios (CBRs) 132 as discrete point to point (PTP) links 204 to bridge remote data access networks (ANs) 208 to a private core network (PCN) 212. Each link 204 requires unobstructed LOS propagation and is limited to a single PTP radio configuration. To the extent that multiple links originate from a common location, the CBRs 132 at such location require spatial and directional separation if co-channel operation is used.
Typically, the operator of the PCN 212 will use an element management system (EMS) 216 specific to particular CBRs 132 to monitor deployed and configured CBR links within the PCN 212. Often, an EMS 216 allows fault monitoring, configuration, accounting, performance monitoring and security key management (FCAPS) for the CBRs 132 within the PCN 212. However, such a conventional EMS 216 does not dynamically modify operational policies or configurations at each CBR 132 in response to mutual interactions, changing network loads, or changes in the radio spectrum environment in the vicinity of the deployed CBRs 132. Furthermore, such an EMS 216 is typically isolated from communications with or coordination amongst other EMSs at other PCNs (not shown) that may be overlapping geographically from a radio spectrum perspective.